1. Field of the Invention
This invention relates to systems and methods for antenna pointing. Particularly, this invention relates to systems and methods for antenna pointing and spacecraft orientation in satellite applications. This invention can also be utilized for: radar applications, missile applications, and other applications where accurate antenna and antenna platform pointing are needed.
2. Description of the Related Art
The need for precision pointing of antenna and instrumentation as well as spacecraft orientation is fundamental to spacecraft development. Thus, various techniques to achieve pointing accuracy have a long history in spacecraft design.
Spacecraft pointing precision for science instrumentation can ordinarily be achieved on the order of approximately 0.5 arc sec. However, when this pointing precision is transferred to the high-gain antenna (HGA), a pointing accuracy of only 0.5 to 1.0-degrees is typically achieved. Accordingly, to further improve the spacecraft pointing of its high gain antenna, a boresight of the high gain antenna against a ground station antenna signal is often conducted. The boresight costs in additional spacecraft fuel, takes a long time (i.e. hours) to complete and must be repeated every so often (every few months) depending on the application and link budget allocation.
Commercial geostationary (GEO) satellites typically employ known monopulse tracking systems to improve the satellites' pointing accuracies towards their designated Earth stations or any required direction. The monopulse system creates a feature (typically a notch) in the antenna far-field pattern, in the co-polarization component of the radiation. The monopulse system increases the spacecraft production cost by few million dollars as well as the satellite weight. The increase in satellite weight correspondingly increases the launch cost and places a limit on the servicable life expectancy of the satellite. The servicable life expectancy of the satellite is limited by the amount of fuel available on board the satellite, and thus its weight, for its designated position slot and as required for station keeping.
In view of the foregoing, there is a need in the art for improved apparatuses and methods for antenna pointing and spacecraft orientation. There is particularly a need for such apparatuses and methods to operate at a minimum cost and weight. Further, there is a need for such apparatuses and methods to be simple, efficient, and affordable. These and other needs are met by embodiments of the present invention as detailed hereafter.